1. Field of the Invention
The present invention relates to a water-dilutable, crosslinkable binder comprised of an acrylate copolymer having as pendant groups water-soluble, half esters of dicarboxylic acid and olefinic groups which can be crosslinked.
2. Background of the Invention
Coating compositions, glues and inks generally contain a binder polymer which can be dried and/or cured to provide a film. Frequently the binder polymer includes reactive groups which are crosslinked during the cure of the composition, to provide an insoluble polymer film.
GB Patent Specification 1,228,040, having a priority date of Aug. 28, 1967, describes a crosslinkable lacquer resin and a process for production thereof. The resin consists of the reaction product of
(A) A copolymer of ethylenically unsaturated monomers, one of which contains an epoxy group, PA1 (B) an aliphatic hydroxycarboxylic acid, and PA1 (C) a cyclic anhydride of a dicarboxylic acid. PA1 (1) a copolymer of a cyclopentadiene type compound and at least one .alpha.,.beta. unsaturated monomer, with PA1 (2) acrylic acid and/or methacrylic acid. PA1 R.sup.2 is C.sub.1 to C.sub.5 alkyl PA1 R.sup.3 is vinyl or allyl PA1 R.sup.4 is C.sub.1 to C.sub.5 hydroxyalkyl PA1 R is the half ester of a dicarboxylic acid capable of forming cyclic anhydride PA1 a is 10 to 100 PA1 b is 0.1a to a PA1 c is 1 to 5 PA1 d is 0.1b to b PA1 e is 0 to b PA1 (1) 5-70% by weight of one or more epoxy group-containing (meth)acrylate compounds PA1 (2) 3-30% by weight of one or more hydroxy-functional (meth)acrylate compounds, and PA1 (3) 0-92% by weight of one or more monomers copolymerizable with (a) and (b) PA1 (1) 5-70% by weight of one or more epoxy group-containing (meth)acrylate compounds, PA1 (2) 3-30% by weight of one or more hydroxy-functional (meth)acrylate compounds, and PA1 (3) 0-92% by weight of one or more monomers copolymerizable with (1) and (2). PA1 R.sup.1 is H or CH.sub.3 PA1 R.sup.2 is C.sub.1 -C.sub.18 PA1 R.sup.3 is C.sub.1 -C.sub.5 hydroxylalkyl PA1 R.sup.4 is ##STR6## with n=0-2 a is 5-10 PA1 b is 2-60 PA1 c is 1-5 PA1 d is 0.2-60 PA1 e is 0-30
Reactant (A) is reacted with reactant (B), wherein the carboxyl group of the hydroxycarboxylic acid reacts with the epoxy groups contained in the copolymer. Subsequently reactant (C) is reacted with the hydroxyl groups which are present due to the addition of the hydrocarboxylic acid to the epoxy groups containing copolymers.
The product produced is said to be surprisingly compatible with aminoplasts, enabling the production of highly concentrated laquer (solvent-based) solutions of relatively low viscosity.
GB Patent Specification 1,227,398, having a priority dated Aug. 16, 1967, discloses air-drying lacquers based on vinyl resins. They are prepared by reacting a copolymer of ethylenically unsaturated monomers, one of which contains an epoxy group, with a drying fatty acid in the presence of a solvent. The fatty acids are linked to the epoxy groups. Subsequently a dicarboxylic acid anhydride is added, which essentially reacts with the hydroxyl groups which originate from the epoxy groups.
U.S. Pat. No. 4,037,038, issued July 19, 1977 (priority filed in Japan on Aug. 5, 1975), describes a resin suitable as a coating material, which resin consists essentially of a reaction product of
The .alpha.,.beta. unsaturated monomer is selected from the group consisting of hydroxy (meth)acrylates, glycidyl (meth)acrylates, allyl glycidyl ether and methallyl glycidyl ether.
The product produced is particularly recommended for use in solvent-free printing inks.
A polymer binder of the type which comprises acrylate copolymers having crosslinkable pendant groups is described in European Patent Specification 0 099 207. For the type of binder polymer described therein, the crosslinkable pendant olefinic groups must not exceed a the degree of reactivity defined in the specification (since otherwise the crosslinking reaction in the presence of radicals will proceed in an uncontrolled manner).
The polymer binder described in European Patent Specification 0 099 207 includes olefinic groups which are, in particular, allyl groups and vinyl groups, such as allyl itaconate or vinyl itaconate. With such pendant crosslinkable groups, the known binders are of the following formula ##STR1## wherein R.sup.1 is H or CH.sub.3
Crosslinking of the polymers of the type described in the above-referenced patent specification is carried out with a catalyst such as a cobalt salt under the influence of oxygen from the air.
At present there is much interest in two-component water-dilutable systems based on acrylate copolymers of the kind described above. However, it is desired to use polyfunctional crosslinking agents which enter into an addition reaction with the olefinic pendant groups rather than crosslinking catalysts such as cobalt salts, which do not enter into the addition reaction, since favourable solvent resistance, hardness, and scratch resistance are more readily obtained with such polyfunctional crosslinking agents than with the conventional systems cured using metallic salts under the influence of oxygen.
The present invention therefore has for its object to provide a water-dilutable binder that may be cured with polyfunctional crosslinking agents.